Fix line-height of admin CSS for .updated and .error messages

Description

This is just a one-line fix to wp-admin/css/global.dev.css. Either bug or enhancement depending on how you rate typography/design/readability.

In 3.0.1 and trunk, the line-height property for error messages is set to 1. These are the pink- and yellow-background messages such as "Settings saved" that are displayed to the user.

The bug is that with line-height set to 1, the leading/line spacing == the font size, so these look horrible when the message wraps more than one line in the browser. The lines of type overlap each other, so it's hard to read. My guess would be that the design tester just wasn't looking at multi-line error messages, or it would have been caught earlier. Short, single-line messages such as "Settings saved." look fine.

To see one, call add_settings_error('some', 'text', 'some text that's long enough to wrap more than one line in the browser') on some admin page.

I've attached a patch with suggested fix to change this property from 1 (i.e. == 100%) to 125%. An alternate fix that I'd be happy with would be to just delete the property (so that line-height would revert to being the same as other <p> elements on the page). As long as line-height is set to some reasonable default value so that I don't have to hardcode style rules into my plugins any more, I will be happy!

More info: The computed font size of .updated p, .error p in the browser is 12px. So, my suggestion of 125% equals leading of 15px. This is slightly narrower than the line spacing of the other <p> elements on the admin page and I believe fits the designer's presumed original intent of compressing the line spacing slightly for these error messages. But again, I would also agree with just deleting the "line-height" property for this style declaration, so that the line spacing for these messages is the same as for other <p>s on the admin pages, and is obviously simpler to just not modify the default line-height at all.